My Ford 7.5 carburated motor is running rough

[Bilito]

Originally Posted by stink

I found on the older 460s number 7 and 8 are next to each other in firing order. Suggest separating the plug wires. If the wires run together, they will crossfire. Number 8 compression may be low because of this misfire. Ford big blocks also had an intake manifold leak issue that you can check by spraying the joining surfaces with carb cleaner while the engine idles. When you find the vacuum leak the engine will smooth out. The egr plate under the carb had a habit of burning thru or warping causing vacuum leak there. You may need to remove carb to remove egr plate and inspect.
Disconnecting the thermactor system will do nothing but increase emissions. No hp gains, no mileage gains. If you decide to disconnect the egr you will get severe pinging under load. Hope this helps.

I want to check the timing, problem is the distributer is well under the firewall and I can neither see it good from inside the cab or figure a way to see from under neither. How do I get a timing light and an eyeball in there to see the pointer, I have felt around in the blind and I cannot find the nut that locks the distributer in place either, I know the timing is between 6 and 8 BTDC, I think the timing might be too far in advance but I want to check for sure, suggestions to get in there would be helpful

[whem2fish]

On a Chevy the timing mark is on the bottom might look

[Bilito]

Originally Posted by Bilito

I want to check the timing, problem is the distributer is well under the firewall and I can neither see it good from inside the cab or figure a way to see from under neither. How do I get a timing light and an eyeball in there to see the pointer, I have felt around in the blind and I cannot find the nut that locks the distributer in place either, I know the timing is between 6 and 8 BTDC, I think the timing might be too far in advance but I want to check for sure, suggestions to get in there would be helpful

Ok we did all the compression checks, cylinders 5 and 8 have 118psi all the rest are at 120.
We did find that by revving up the motor and holding it for 5 or 10 seconds the shaking got worse and it backfired a few times
Thoughts about that???

[Bilito]

Originally Posted by Bilito

Ok we did all the compression checks, cylinders 5 and 8 have 118psi all the rest are at 120.
We did find that by revving up the motor and holding it for 5 or 10 seconds the shaking got worse and it backfired a few times
Thoughts about that???

We also connected a vacuum gauge, it read very steady at the top of the green about 23 inch of vac.

[Dave78Chief]

Thoughts about that???

Cylinder missing or not firing in the correct sequence

Sounds more like crossed wires or timing not set right to me.

A repost


You will most likely have to crawl inside the right side wheel well to see the timing mark on the harmonic ballancer (ignore the writing on the pic).


Note: Engine backfiring can result in the Power Valve in the Holley Carburetor getting blown out. Results in the engine running to rich.

Dave

[Bilito]

Originally Posted by Dave78Chief

Cylinder missing or not firing in the correct sequence

Sounds more like crossed wires or timing not set right to me.

A repost


You will most likely have to crawl inside the right side wheel well to see the timing mark on the harmonic ballancer (ignore the writing on the pic).


Note: Engine backfiring can result in the Power Valve in the Holley Carburetor getting blown out. Results in the engine running to rich.

Dave

WOW I never had this diagram, I crawled under and found the marks on the balancer, sanded them a bit and found a faded white line right across 8 degrees BTDC. I can only see the bottom of the pointer, it is directly behind the alternator and is impossible to see or get a timing light on it unless I remove the alternator, I still have not located to distributer lock bolt, I have to do it by feel as the distributer is almost out of reach.
Is it ok to remove the alternator to time the motor?

[Bilito]

Originally Posted by Bilito

WOW I never had this diagram, I crawled under and found the marks on the balancer, sanded them a bit and found a faded white line right across 8 degrees BTDC. I can only see the bottom of the pointer, it is directly behind the alternator and is impossible to see or get a timing light on it unless I remove the alternator, I still have not located to distributer lock bolt, I have to do it by feel as the distributer is almost out of reach.
Is it ok to remove the alternator to time the motor?

BTW all the lines with white dashes are part of the emissions system that is disconnected because both air pumps are Kaput

[Dave78Chief]

Get yourself an inspection mirror from the auto supply. Helps to locate those missing elements easier.

Yes you can remove the alternator however you will also have to remove the fan belt to do that so it does not get torn up. From what I see in the JD manual that might not be a lot of fun.

Dave

[Bilito]

Originally Posted by Dave78Chief

Get yourself an inspection mirror from the auto supply. Helps to locate those missing elements easier.

Yes you can remove the alternator however you will also have to remove the fan belt to do that so it does not get torn up. From what I see in the JD manual that might not be a lot of fun.

Dave

I have a mirror, unfortunately it is broken, gotta get a new one. we found, or rather felt a nut below the distributor body, we loosened it with one of those weirdly bent distributer wrench's, cannot move the unit. Do you have a picture of how that thing is held in place? About how much should I be able to move the dist one way or the other?

This has got to be out of time or I have some wires crossed, I have checked the firing order about a half dozen times. it sure has me puzzled

[Dave78Chief]

Distributor is just stuck or you have not loosened the hold down clamp bolt enough. This is a picture of a EFI setup but the distributor bolt should be in the same place.


You have what is reffered to as Ford Duraspark 2 electronic ignition system.


Some possible sources of your problem are:
Ignition coil

Distributor pick-up (You can see vacuum advance can attached to the distributor in this picture).


or,
Ignition Module (get tested at an someplace like Autozone)


Description: Duraspark II -- The Ford V-8 Engine Workshop

Troubleshooting Information for various issues: Troubleshooting your ignition system - Ford Muscle Forums : Ford Muscle Cars Tech Forum

Make sure rotor is in good condition
Make sure the distributor cap is not cracked and does not exhibit carbon tracking
Make sure the distributor vacuum advance is working properly. It varies engine timing based on engine load (vacuum controlled).
I suspect there are centrifugal advance weights in the distributor below the pickup plate. They have to move freely without binding. They advance the timing based on engine RPM.

Poor performance and operation can result from any of these components breaking down.

Dave

[stink]

while the engine is running at idle put your hand partially over the carb primary. This will be the front two bores with the choke housing. while just partially cutting off some of the air the engine gets if the engine runs better its running lean, most likely a vacuum leak (egr plate, intake, hoses or maybe brake booster) If the engine emidiatly (spelling) dies than its running rich. Carb float adjustment, idle to rich and yes there are idle mixture screws and they may not have been exposed as some were sealed at the factory. If the engine starts to stumble more than you have a possible ignition problem. You may have a defective pickup coil in the distributor or a cracked reluctor ring. This can be found with an old school manual ignition analyzer. A new distributor may be less expensive than a trip to the diagnostic shop.

[Bilito]

Originally Posted by stink

while the engine is running at idle put your hand partially over the carb primary. This will be the front two bores with the choke housing. while just partially cutting off some of the air the engine gets if the engine runs better its running lean, most likely a vacuum leak (egr plate, intake, hoses or maybe brake booster) If the engine emidiatly (spelling) dies than its running rich. Carb float adjustment, idle to rich and yes there are idle mixture screws and they may not have been exposed as some were sealed at the factory. If the engine starts to stumble more than you have a possible ignition problem. You may have a defective pickup coil in the distributor or a cracked reluctor ring. This can be found with an old school manual ignition analyzer. A new distributor may be less expensive than a trip to the diagnostic shop.

I have followed everyones advice with the following results
moved the #7 and #8 leads far apart...No Change
swapped the #7 and #8 leads and it got really bad
Hand over intake, it wanted to suck my hand in and no change
I see this carb has float adjusters, I will check that both bowls have the correct level of fuel

If I remove the two air pumps and the alternator I will have access to the distributer base and then can see the timing pointer
I will order a rebuild kit from Holley when I can find the model number on the carb, I know it is on the back of the air intake but my handy dandy mirror is broken

Could the ignition coil be causing this misfiring?

All this emission junk is in the way of doing everything and according to All I have read about this type of system it is questionable if it actually reduced emissions much if at all. All it does is pump fresh air mixed with some exhaust air back into the air cleaner where it mixed with outside air and under the hood air to go thru the air filter and get re-burnt. It satisfied some regulation back in 1991

[whem2fish]

Most holly carbs the number will be on the front of the air horn for the power valve you need the correct one. With trans in gear motor running see go much vacumm you have then subtract 2 this will give you the correct one it will be stamped on the side of the valve

[Bilito]

Originally Posted by whem2fish

Most holly carbs the number will be on the front of the air horn for the power valve you need the correct one. With trans in gear motor running see go much vacumm you have then subtract 2 this will give you the correct one it will be stamped on the side of the valve

I called Holly, from all the numbers I found they said I have a 4180 carb and the renew kit is #3-1346. I tried locally and only one store had it for 95 bucks, Holly wants 51.00. I will order it from Holly on Monday.
I was told what I was already told here, a bad power valve would cause a rough idle, rich running and a backfire thru the exhaust. They said I most likely will have a combo of issues, clogged passages and a faulty power valve and they sternly said I should make absolutely sure the timing is correct. I guess I am on the right path.

My wife and I got one of the air pumps out, the next one is gonna be a bear, it is hidden behind this monster bracket that the air pump was attached to and the alternator is also hanging on this bracket. Once I get both pumps and the alternator out I will have access to the distributer. Talk about working with just your fingertips and I had to knell in the wheel well and lean on the tire to work a ratchet and I could only get one or two clicks at a time, it took about 45 min to remove one rusted and almost impossible to reach bolt, the pivot bolt was even harder, will try to get the rest out tomorrow or the next day